JP2008017012A - Communication apparatus and information apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication apparatus and an information apparatus which prevents the null event occurring originally at an specific distance to result in that a stable and high-reliability IC card communication is realized. <P>SOLUTION: When an error detector circuit 240 detects a signal error, the detector circuit controls the inductance L11 of an antenna coil 211, the capacitance C11 of a capacitor 213, and any values of a coil, a capacitor, and a resistor in an RLC matching circuit, of constituent elements in an antenna circuit 210 relating to communication, so as to change any of element values to a specified level. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication device capable of communicating with a non-contact type IC card and information equipment such as a personal computer and a mobile phone.

  The development of IC card technology in recent years is remarkable, and it has been used conveniently in various fields such as railway tickets, purchase of goods, and entry / exit management.

  Many of these systems do not have a battery on the IC card side, and operate the IC card by non-contact power feeding by electromagnetic waves sent from a reader / writer (hereinafter referred to as R / W) side ( For example, see Patent Documents 1, 2, and 3).

The application system requires bidirectional data transmission from the R / W to the IC card (downstream) and from the IC card to the R / W (upstream) direction.
In the downstream direction, the purpose is achieved by ASK (Amplitude sift keying) modulation of the carrier transmitted from the R / W.

On the other hand, in the upward direction, the IC card does not have a power source and does not have a function of transmitting a carrier from itself.
For this reason, the IC card receives the carrier transmitted from the R / W by the load resistance connected to the tuning circuit of the inductor L and the capacitor C, and the load resistance corresponding to “1” / “0” of the transmission data. The data transmission function is realized by a so-called “load modulation method” in which the value of the signal is changed.

On the R / W side, it is detected as a voltage change of the antenna coil that occurs in response to a change in the value of the load resistance on the IC card side, and uplink data is reproduced.
Japanese Patent No. 3488166 JP 2004-356765 A JP 2005-136944 A

The “load modulation method” has the advantage that data transmission in the upstream direction can be realized with a simple configuration even from an IC card without a battery, but on the other hand, it is a method of switching the load of the L / C coupling circuit. For this reason, in principle, load modulation is not performed at a specific distance, so-called “null phenomenon” occurs, and inconvenience occurs that communication in the upstream direction cannot be performed.
The null phenomenon will be described below with reference to the drawings.

  FIG. 1 shows a principle configuration example of the R / W and the IC card.

As shown in FIG. 1, the R / W 1 includes an antenna coil 11, a series resistance component 12 of the antenna coil 11, a capacitor 13 connected in parallel to the antenna coil 11, a matching circuit 14, and a carrier signal source (OSC) 15. Have.
The IC card 2 includes an antenna coil 21, a series resistance component 22 of the antenna coil 21, a capacitor 23 connected in parallel to the antenna coil 21, and a load resistor 24 connected in series connected in parallel to the antenna coil 21 and the capacitor 23. , 25 and a switch (SW) 26 connected to both ends of the load resistor 25.
L1 represents the inductance of the antenna coil 11, R1 represents the resistance value of the resistance component 12, and C1 represents the capacitance of the capacitor 13.
Similarly, L2 represents the inductance of the antenna coil 21, R2 represents the resistance value of the resistance component 22, C2 represents the capacitance of the capacitor 23, RL represents the resistance value of the load resistor 24, and RL ′ represents the resistance value of the load resistor 25. , Respectively.

The OSC 15 on the R / W 1 side is a carrier signal source having an oscillation frequency fc of 13.56 MHz, for example, and drives a parallel resonance circuit of the antenna coil 11 and the capacitor 13 via the matching circuit 14.
Although the matching circuit 14 can be configured as an RLC matching circuit, FIG. 1 shows an example in which the matching circuit 14 is configured by only one element of the capacitor 14a having the capacitance Ct.

The antenna coil 11 on the R / W1 side and the antenna coil 21 on the IC card 2 side are electromagnetically coupled with a coupling coefficient k.
The coupling coefficient k is a value depending on the distance between R / W1 and the IC card 2, and k = 0 when the distance = ∞.

On the IC card 2 side, a carrier sent from the R / W 1 is extracted by a parallel resonance circuit including an antenna coil 21 and a capacitor 23 and terminated with load resistors 24 and 25.
The switch 26 provided in the IC card 2 is a load modulation changeover switch, and performs an “on” / “off” operation according to “1” / “0” of the input of the load modulation signal LMS. Do.
That is, when the switch 26 is “on”, the load resistance is only the resistance 24 (RL), and when it is “off”, the load resistance changes to the resistances 24 and 25 (RL + RL ′). The load impedance on the IC card 2 side changes, and the change is detected as a change in the voltage V1 across the antenna coil 11.
However, the relationship between the change in the load resistance RL and the change in the voltage V1 at both ends of the antenna coil 11 is not uniform, and greatly depends on the value of the distance ∝ coupling coefficient k.

2A to 4B conceptually show the relationship between the load modulation signal LMS and the voltage V1 across the antenna coil 11 on the R / W1 side.
2A to 4A show the waveform of the voltage V1 across the antenna coil 11 on the R / W1 side, and FIG. 2B to FIG. 4B show the load modulation signal LMS. sw-on indicates that the switch 26 of the IC card 2 is in the on state, and sw-off indicates that the switch 26 is in the off state.

FIGS. 2A and 2B show the voltage V1 when the load resistance value RL and the voltage V1 at both ends of the antenna coil 11 change in the positive phase, that is, when the load resistance value RL decreases. Is also smaller.
This corresponds to the case of k = 0.15 when configured with each element value described later, for example.

4A and 4B show the voltage V1 when the load resistance value (RL) and the voltage V1 at both ends of the antenna coil 11 change in opposite phases, that is, when the load resistance value RL becomes small. Is a case where
This corresponds to, for example, the case of k = 0.25 when configured with each element value described later.

3A and 3B show a case where the value of the voltage V1 across the antenna coil 11 does not change even when the value of the load resistance (RL) changes, that is, the null state.
This corresponds to the case where k = 0.2, which is intermediate between FIG. 2A and FIG.

In the case of FIG. 2A and FIG. 4A, although there is a difference between the positive phase and the reverse phase, the amplitude of the voltage V1 changes corresponding to “1” / “0” of the load modulation signal. Therefore, if the spiral line is demodulated as an ASK (Amplitude Shift Keying) signal, the original signal can be reproduced on the R / W1 side.
However, in the null state of FIG. 3A, the amplitude of the voltage V1 remains constant and does not change, so that signal demodulation on the R / W1 side is impossible.

FIG. 5 shows a load modulation waveform detected on the R / W side when fc = 13.56 MHz, Ct = 40 pF, C1 = 30 pF, L1 = 1530 nH, L2 = 1200 nH, RL = 1 kΩ, that is, a change in V1 = The state of ΔV1 is shown.
In FIG. 5, the horizontal axis indicates the coupling coefficient k, and the vertical axis indicates the change in voltage V1 when the card-side load resistance value RL is slightly changed = ΔV1 as a relative value.
In FIG. 5, the white circle portion indicates that the voltage V1 decreases when the load resistance value RL is reduced (normal phase), and the black circle portion indicates that the voltage V1 is reversed when the load resistance value RL is reduced. It represents an increase (reverse phase).

In the figure, point A is k = 0.15, and the relationship between RL change and ΔV1 is positive phase, which corresponds to the case of FIG.
The point C is k = 0.25, and the relationship between the RL change and ΔV1 is in reverse phase, which corresponds to the case of FIG.
Point B is k = 0.2, and V1 is a null point that does not change even if RL changes. This corresponds to the case of FIG.

  An object of the present invention is to provide a communication device and an information device that can prevent a null phenomenon that occurs originally at a specific distance and, as a result, can realize stable and highly reliable IC card communication.

  A communication device according to a first aspect of the present invention includes an antenna circuit including at least an antenna inductor as a constituent element related to communication, and a carrier having a predetermined frequency connected to the antenna circuit to drive the antenna inductor of the antenna circuit. A carrier signal source to be generated, a signal receiving circuit for receiving and demodulating a signal induced in the antenna inductor, and an error detecting circuit having a function of detecting a signal error of a demodulated output of the signal receiving circuit, The antenna circuit is formed so that at least one element value of the constituent element can be changed, and the error detection circuit is configured to be configured to change at least one of the constituent elements involved in communication of the antenna circuit when a signal error is detected. Control to change the value by a predetermined amount.

  A second aspect of the present invention is an information device having an information processing function, including a communication device having a reader / writer function, and the communication device includes an antenna circuit including at least an antenna inductor as a constituent element related to communication; A carrier signal source connected to the antenna circuit for driving the antenna inductor of the antenna circuit and generating a carrier of a predetermined frequency, a signal receiving circuit for receiving and demodulating a signal induced in the antenna inductor, and the signal An error detection circuit having a function of detecting a signal error in the demodulated output of the reception circuit, wherein the antenna circuit is formed such that at least one element value of the constituent elements can be changed, and the error detection circuit includes a signal When an error is detected, at least one of the constituent elements involved in the communication of the antenna circuit is selected. Controlling the value so that a predetermined amount changes.

  Preferably, the error detection circuit determines whether or not the waveform quality of the demodulated signal of the signal receiving circuit is good, and controls to change the element value by a predetermined amount when it is determined that the waveform quality is not good. To do.

  Preferably, the error detection circuit determines whether or not there is an error in the data in the received signal, and controls to change the element value by a predetermined amount when there is a data error.

  Preferably, the error detection circuit determines that reception has failed from the contents / history of signal transmission / reception, and controls to change the element value by a predetermined amount when it is determined that reception has failed.

  Preferably, the error detection circuit determines whether or not the waveform quality of the demodulated signal of the signal receiving circuit is good, and controls to change the element value by a predetermined amount when it is determined that the waveform quality is not good. A first processing unit that determines whether there is an error in the data in the received signal, and a second processing unit that controls to change the element value by a predetermined amount when there is a data error, and a signal At least one of the third processing units that controls the element value to be changed by a predetermined amount when the reception failure is determined from the content / history of the transmission / reception of and when the reception failure is determined Part.

  Preferably, the antenna circuit includes a tuning capacitor that forms a tuning circuit with the antenna inductor, and the error detection circuit detects an inductance of the antenna inductor and a capacitance of the tuning capacitor when a signal error is detected. Of these, at least one of the values is controlled to change by a predetermined amount.

  Preferably, the antenna circuit includes a matching circuit connected to the antenna inductor and the carrier signal source, and the matching circuit includes at least one component of an inductor, a capacitor, and a resistor, and the error When detecting a signal error, the detection circuit changes at least one of the inductance of the antenna inductor, the capacitance of the tuning capacitor, and the element value of at least one component of the matching circuit by a predetermined amount. To control.

  According to the present invention, it is possible to prevent a null phenomenon that originally occurs at a specific distance, and as a result, it is possible to realize stable and highly reliable IC card communication.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 6 is a diagram illustrating a configuration example of a communication system to which a mobile phone as a portable information device according to an embodiment of the present invention is applied.

  A communication system 100 shown in FIG. 6 includes a mobile phone 110, an external non-contact type IC card 120, a base station 130, a communication network 140, and a server 150.

The cellular phone 110 according to the present embodiment has, for example, a built-in R / W (reader / writer) function, and the mounted R / W function receives a response (signal) from the external non-contact type IC card 120. Then, wireless communication is performed with the non-contact type IC card 120 to establish a connection.
When the connection with the non-contact type IC card 120 is established, the mobile phone 110 is connected to the server 150 from the base station 130 via the communication network 140 by wireless communication according to a predetermined communication method. The communication between 120 and the server 150 is relayed.
If the mutual authentication is successful, the R / W function installed in the mobile phone 110 reads the information stored in the non-contact type IC card 120 in accordance with an instruction from the server 150, or the non-contact type IC card. A process of writing new information in 120 is performed.

  FIG. 7 is a block diagram illustrating a basic configuration example of the mobile phone according to the present embodiment.

  As shown in FIG. 7, the cellular phone 110 includes a wireless communication unit 111 that performs wireless communication processing with the server 150 via a communication network 140, a display unit 112 including a liquid crystal display device (LCD), a numeric keypad, and the like. An operation unit 113 including operation keys, a voice processing unit 114 having a microphone and a speaker for performing voice input processing or voice output processing, a memory unit 115 for storing programs, message data, address data, IC card data, and the like, R The communication device 116 forming the front end circuit unit for realizing the / W function, and the mode control, transmission data TD, and reception data RD for realizing the overall function control and R / W function of the mobile phone 110 A control unit (CPU) 117 that performs predetermined processing and access to the memory unit 115 according to the predetermined process is included.

The wireless communication unit 111, the display unit 112, the operation unit 113, the voice processing unit 114, the memory unit 115, and the control unit 117 constitute a telephone unit as a normal mobile phone.
The communication device 116, the memory unit 115, and the control unit 117 constitute a card function unit that realizes the R / W function.
In addition, the mode designation, switching, and the like can be configured to be performed by the control of the control unit 117 according to the operation of the operation unit 113.
At this time, the control unit 117 outputs, for example, a control signal and transmission data TD to the communication device 116, receives the reception data RD, and performs storage processing in the memory unit 115. The memory unit 115 includes a nonvolatile memory such as a flash memory.
The control unit 117 may be configured to be provided separately for the telephone unit and the card function unit.

FIG. 8 is a diagram showing a configuration example of a communication device with a built-in R / W function mounted on the mobile phone according to the embodiment of the present invention.
In FIG. 8, the communication device 116 of FIG.

8 includes an antenna circuit (antenna front end) 210, a carrier signal source (OSC) 220 that generates a carrier having an oscillation frequency fc of 13.56 MHz, a signal reception circuit 230, and an error detection circuit 240. However, a part of the R / W function is realized by these components.
The OSC 220 of the communication device 200 drives a parallel resonance circuit of the antenna coil 211 and the capacitor 213 via the matching circuit 214.
According to this embodiment, since the output impedance of the R / W transmission circuit is switched according to the communication state, even if there are a plurality of types of IC cards facing each other or the distance from the IC card changes, it is stable. Proximity wireless communication is possible.

As shown in FIG. 8, the antenna circuit 210 includes an antenna coil 211, a series resistance component 212 of the antenna coil 211, a capacitor 213 connected in parallel to the antenna coil 211, and a matching circuit 214 formed by, for example, a capacitor 214a. .
Although the matching circuit 214 can be configured as an RLC matching circuit, FIG. 8 shows an example in which the matching circuit 214 is configured by only one element of the capacitor 214a having the capacitance Ct.
A node ND1 is formed by a connection point of one end of the resistor 212, one electrode of the capacitor 213, and the matching circuit 214t, and the node ND1 is connected to an input of the signal receiving circuit 230.
In the figure, L11 represents the inductance of the antenna coil 211, R11 represents the resistance value of the resistance component 212, C11 represents the capacitance of the capacitor 213, and Ct represents the capacitance of the capacitor 214a of the matching circuit 214.

  In FIG. 8, the inductance L11 of the antenna coil 211, the resistance value R11 of the resistance component 212, the capacitance C11 of the capacitor 213, and the capacitance Ct of the capacitor 214a of the matching circuit 214 are at least one by a control signal from the error detection circuit 240 indicated by a broken line. This is shown as adjustable, for the following reason.

In the upward direction communication of the proximity IC card (from the IC card to the R / W direction), so-called load modulation is performed in which data communication is performed by changing the voltage at the antenna coil end of the R / W by switching the load resistance value in the card. Although it is adopted, there is a distance (null point) where load modulation is theoretically not applied.
In the present embodiment, in order to avoid this null point, the R / W side error detection circuit 240 checks the quality of the received waveform, and when it is determined that the quality has deteriorated, the antenna coil 211, the resistance component 212, and the capacitor 213. The communication quality is improved by changing the value of either the antenna tuning circuit formed by the above or the LCR element of the matching circuit 214 so as to escape the null point.
For this purpose, at least one of the inductance L11 of the antenna coil 211, the resistance value R11 of the resistance component 212, the capacitance C11 of the capacitor 213, and the capacitance Ct of the capacitor 214a of the matching circuit 214 is at least one by a control signal from the error detection circuit 240 indicated by a broken line. One is shown as adjustable.
In other words, when the error detection circuit 240 detects a signal error, for example, the inductance L11 of the antenna coil 211, the capacitance C11 of the capacitor 213, and the element value of any of the coil, capacitor, and resistance of the RLC matching circuit are changed by a predetermined amount. Control.
Any one of the variable parameters such as inductance, capacitance, and resistance value may be used, or two or more parameters may be combined to be variable.
Hereinafter, as an example, a case will be described as an example in which control is performed so as to escape the null point by changing the capacitance Ct of the capacitor 214a of the matching circuit 214.

  FIG. 9 is a circuit diagram showing a configuration example of the IC card according to the present embodiment.

The IC card 120 also includes an antenna coil 121, a series resistance component 122 of the antenna coil 121, a capacitor 123 connected in parallel to the antenna coil 121, and a load resistor 124 connected in series connected in parallel to the antenna coil 121 and the capacitor 123. , 125 and a switch (SW) 126 connected to both ends of the load resistor 125.
9, L12 is the inductance of the antenna coil 121, R12 is the resistance value of the resistance component 122, C12 is the capacitance of the capacitor 123, RL is the resistance value of the load resistor 124, and RL ′ is the resistance value of the load resistor 125. Respectively.

In the communication device 200 (116) of the mobile phone 110, the antenna coil 211 and the antenna coil 121 on the IC card 120 side are electromagnetically coupled with a coupling coefficient k.
The coupling coefficient k is a value that depends on the distance between the communication device 200 (R / W) side and the IC card 120, and k = 0 when the distance = ∞.

On the IC card 120 side, a carrier sent from the communication device 200 (R / W) is extracted by a parallel resonance circuit including an antenna coil 121 and a capacitor 123 and terminated with load resistors 124 and 125.
The switch 126 provided in the IC card 120 is a load modulation changeover switch, and performs an “on” / “off” operation according to “1” / “0” of the load modulation signal LMS input. Do.
That is, when the switch 126 is “on”, the load resistance is only the resistor 124 (RL). When the switch 126 is “off”, the load resistance changes to the resistors 124 and 125 (RL + RL ′). The load impedance on the IC card 120 side changes, and the change is detected as a change in the voltage V1 across the antenna coil 211.
However, the relationship between the change in the load resistance RL and the change in the voltage V1 at both ends of the antenna coil 211 is not uniform, and greatly depends on the value of the distance ∝ coupling coefficient k.

Now, the description returns to the configuration of FIG.
The signal receiving circuit 230 receives the voltage V1 of the node ND1 generated by receiving the load modulation signal from the IC card 120 side by the antenna coil 211 and inputs the amplitude change ΔV1 (hollow line) to digital “1” / ”. It includes an ASK demodulating circuit that converts it to a 0 "signal.
This ASK demodulation circuit can be easily configured by various techniques.

  The error detection circuit 240 has a function of checking the ASK demodulated waveform of the signal reception circuit 230 and determining whether or not a predetermined quality is satisfied. For example, when a signal error is detected, the inductance L11 and the capacitor 213 of the antenna coil 211 are detected. A control signal S240 is output to a predetermined variable element of the antenna circuit 210 for controlling the element value of any one of the capacitor C11, the coil of the RLC matching circuit 214, the capacitor, and the resistance to be changed by a predetermined amount.

  The error detection judgment items in the error detection circuit 240 generally include received signal jitter, duty, synchronization error, cyclic code error, etc., but other items may be used.

  The error detection circuit 240 changes the parameters of the antenna circuit (antenna / front end) (element values of any of the coils, capacitors, and resistors of the “L1”, “R1”, “C1”, or “RLC matching circuit”). The control method to be performed is roughly divided into the following three methods. In the following description, the parameter of the element to be controlled will be described as a front end parameter.

1): Determine whether the waveform quality of the ASK baseband demodulated signal is good or not, and control the front-end parameters (first determination criterion).
2): A data error in the received packet data is determined, and the front-end parameter is controlled (second determination criterion).
3): Reception failure is determined from the contents / history of transmission / reception, and front-end parameters are controlled (third determination criterion).

It is also possible to control the front end parameter by combining these first, second and third determination criteria in a composite manner.
Hereinafter, the determination criterion will be described in more detail.

Prior to the description of the determination criteria, a packet format applied to the proximity IC card communication will be described.
FIG. 10 is a diagram illustrating a format example of packet data applied to proximity IC card communication.

  This packet 300 has a prefix code area (Preamble) 310 containing at least 48 bits of logical 0 data, a 2-byte synchronization code area (SYNC) 320, and an 8-bit length in which the length of the payload is set. An area (Length) 330, a payload area (Payload) 340 including n byte areas, and a cyclic redundancy check area (CRC) 350 are formed.

<First criteria>
In the first determination criterion, the waveform quality of the ASK baseband demodulated signal is determined, and the front-end parameter is controlled.
The error detection circuit 240 feeds back the determination regarding the waveform quality of the ASK baseband demodulated signal at the time of reception using the first determination criterion, and controls the front-end parameter of the antenna circuit 210 to control the radio reception environment. This stabilizes the received waveform quality in a good state and enables normal reception.

For example, when a Manchester code is employed as a transmission line code, when the waveform of the ASK baseband demodulated signal of the received signal is monitored (sampled), a low (L) width that is too long in terms of the bit rate When there is a high (High: H) width, and a low width and a high width that are too short, it can be determined that demodulated data with good quality as a Manchester code is not obtained.
Specifically, when the bit rate is 212 kbps (about 4.7 μs per bit), the Low width and the High width should be within a length (time) of about 2.3 μs to 4.8 μs, and the waveform When monitoring (sampling), if it deviates from this, it can be determined that a high-quality Manchester code waveform is not obtained.

  FIGS. 11A and 11B are diagrams illustrating an example of the determination logic of the quality of the Manchester code waveform. FIG. 11A shows a high-quality Manchester code waveform, and FIG. 11B shows the quality. A bad Manchester code waveform is shown.

In the case of the Manchester code waveform with good quality shown in FIG. 11A, the error detection circuit 240 has a high number of consecutive high-level and low-level sampling values (corresponding to widths) of 3 to 6 and a good reception waveform quality. It is determined that
In the case of the Manchester code waveform with poor quality shown in FIG. 11B, the error detection circuit 240 has 1 to 8 consecutive numbers (corresponding to widths) of the high level and low level of the sampling value, and the received waveform quality is not good. It is determined that it is in a state.

Actually, when the received baseband demodulated signal is monitored in the “null” state, which is a problem, the Low width and High width do not fit within the specified length (time), and are not fully compliant with the Manchester code format. In many cases, a waveform is shown, and it can be determined that a Manchester code waveform with good quality is not obtained.
On the other hand, when the received baseband demodulated signal is monitored in the “non-null (normal)” state, the correct Manchester code waveform in which the Low width and High width are within the specified length (time) is displayed and is normal. Reception is possible.

The communication device 200 adopting the first determination criterion monitors (samples) the waveform of the ASK baseband demodulated signal at the time of reception, feeds back information and determination regarding the waveform quality of the Manchester code, and sets the parameters of the antenna front end. By controlling the wireless reception environment, the quality of the Manchester code waveform at the time of reception is stabilized in a good state, and normal reception is possible.
More specifically, when the waveform is monitored (sampled) for a certain period (eg several bit rate period) and the Low width and High width are not within the specified length (time), the antenna front end The parameter is switched to a state different from the current state, and the waveform is monitored (sampled) again to determine whether it conforms to the regulations.
By this repetitive control, the parameters are finally fixed and stabilized so as to realize a state of good waveform quality.

  FIG. 12 is a diagram illustrating an example of front-end parameter control based on data waveform quality determination.

  In addition, when this parameter is fixed and stabilized to a parameter that can realize a state of good waveform quality by this repetitive control, in the case of a format in which a prefix code is added as a communication packet structure, that prefix is used. If the parameter control can be completed sufficiently during the code (preamble) period, the parameter setting is completed and fixed during that period, as shown in FIG. A stable wireless reception environment is maintained by preventing changes.

<Second criteria>
In the second determination criterion, a data error in the received packet data is determined, and the front-end parameter is controlled.
The error detection circuit 240 feeds back a determination related to error detection of received packet data using the second determination criterion, and controls the front-end parameter of the antenna circuit 210 to control the radio reception environment, thereby receiving the received waveform. It stabilizes the quality in a good state and enables normal reception.

  Normally, error detection codes such as CRC (Cyclic Redundancy Check), parity check, and checksum are added to this type of packet data as described above. By checking these codes, it can be determined whether the data has been received correctly.

Actually, in the “null” state, which is a problem, it is often found that there is an error in the received packet data as a result of checking the error detection code in the packet data on the receiving side, so that the data can be received correctly. It can be determined that it is not.
Conversely, in the “non-null” state, as a result of checking the error detection code in the packet data on the receiving side, no error occurs and normal reception is possible.

  The communication apparatus 200 adopting the second determination criterion feeds back information and determination regarding error detection of received packet data, controls the antenna / front end parameters, and controls the radio reception environment, so that the next reception time Thus, normal data reception is possible without the occurrence of data errors.

  FIG. 13 is a diagram illustrating an example of front-end parameter control based on data error detection determination.

More specifically, as shown in FIG. 13, when it is determined that a data error has occurred as a result of checking the error detection code in the packet data on the receiving side in one packet reception, the antenna front The end parameter is switched to a state different from the current state to prepare for the next reception.
On the other hand, if the error detection code is inspected in one packet reception and it is determined that there is no data error, the parameters are maintained as they are to prepare for the next reception.
This repeated control maintains a stable wireless reception environment.

<Third criteria>
In the third determination criterion, reception failure is determined from the contents / history of transmission / reception, and the front-end parameters are controlled.
The error detection circuit 240 monitors the contents / history of packet data transmission / reception between the R / W (reader / writer) and the counter IC card 120 using the third determination criterion, and transmits the packet data from the counter IC card 120 to the packet data. When the receiving circuit 230 cannot receive the signal during the period in which it is expected to be returned, the error detection circuit 240 determines that the reception is unsuccessful, and feeds back the determination to the front-end parameter of the antenna circuit 210. By controlling the radio reception environment by controlling the above, the reception waveform quality is stabilized in a good state, and normal reception is enabled.

Normally, as described above, this type of packet data is added with a communication start identification code (synchronization code: SYNC) defined by regulations. By detecting this, the reception side detects the packet data. By specifying the start point, the entire packet data can be received correctly.
However, if the wireless reception environment is extremely bad, the communication start identification code (synchronization code) cannot be detected, and even whether there is a reply from the opposite side cannot be recognized.
In this case, even the presence of a reply itself cannot normally be recognized, so that it is more serious than the case of data error detection described above.
Actually, in the “null” state where there is a problem, there is a case where reception cannot be started because the identification code for starting communication cannot be detected on the receiving side even though there is a reply from the counter IC card 120 side. I know.

  FIG. 14 is a diagram illustrating an example of front-end parameter control based on reception failure determination.

The communication device 200 adopting the third determination criterion monitors the transmission / reception contents / history of packet data between the R / W (reader / writer) and the counter IC card 120, and the packet data is returned from the counter IC card 120. If the error detection circuit 240 cannot detect the communication start identification code during the expected period, it is determined that reception has failed. In that case, the error detection circuit 240 switches the front end parameter of the antenna circuit 210 to a state different from the current state to prepare for the next reception. Conversely, if the reception is successful, the parameters are maintained in the current state to prepare for the next reception.
This repeated control maintains a stable wireless reception environment.

More specifically, it is determined that reception has failed according to the following criteria.
-When "polling", which is the first packet transmission of the entire intercommunication, is sent, if the packet cannot be received within the specified timeout time (the start identification code of the reply packet cannot be detected),
・ If the packet cannot be received even if the transmission is repeated several times (equivalent number) (the start identification code of the reply packet cannot be detected)
It is.

  FIG. 15 is a block diagram illustrating a configuration example of the error detection circuit according to the present embodiment.

  The error detection circuit 240 in FIG. 15 is configured to be able to cope with the case where the above-described first determination criterion, second determination criterion, and third determination criterion are employed.

  Specifically, the error detection circuit 240 includes a data shaper 241, a packet synchronization code detector 242, a packet data output unit 243, an intra-packet data error detector 244, and a front end parameter adjuster 245.

The data shaper 241 includes a data phase detector 2411 and a data waveform quality determiner 2412.
The data phase detector 2411 detects the phase of the received packet data that has been ASK demodulated by the signal receiving circuit 230 and outputs the detected phase to the packet synchronization code detector 242.
The data waveform quality determiner 2412 receives the received packet data that has been ASK demodulated by the signal receiving circuit 230, determines the quality of the waveform quality of the ASK baseband demodulated signal according to the first determination criterion that has already been described in detail, and The determination result is output to the front end parameter adjuster 245 as a signal S2412.

The packet synchronization code detector 242 receives the packet data from the data phase detector 2411, determines the reception failure from the contents (or history) of transmission / reception according to the third determination criterion described in detail, and determines the determination result. The signal S242 is output to the front end parameter adjuster 245.
The packet synchronization code detector 242 detects the synchronization code SYNC in the packet data, and determines that reception has failed when the synchronization code cannot be detected.
The packet synchronization code detector 242 detects the synchronization code SYNC in the packet data. If the synchronization code can be detected, the packet synchronization code detector 242 determines that the reception has not failed and outputs the packet data to the packet data output unit 243.

  The packet data output unit 243 outputs the received packet data to the intra-packet data error detector 244 and also outputs it to the control unit 117.

  The in-packet data error detector 244 receives the packet data from the packet data output unit 243, determines whether there is an error in the received packet data in accordance with the second determination criterion described in detail above, and the like. The determination result is output to the front end parameter adjuster 245 as a signal S244.

  When the determination signal S2412 of the data waveform quality determination unit 2412 indicates that the waveform quality of the ASK baseband demodulated signal is poor, the front end parameter adjuster 245 determines that the detection signal S242 of the packet synchronization code detector 242 If the packet data received by the determination signal S244 of the in-packet data error detector 244 has an error, it is assumed that the packet is in a null state. The control signal S240 is output to the antenna circuit 210, and the front end parameter is adjusted so as to change by a predetermined value.

  The first processing unit includes a front end parameter adjuster 245 and a data waveform quality determiner 2412, and the second processing unit includes a front end parameter adjuster 245 and an intra-packet data error detector 244. The third processing unit includes a front end parameter adjuster 245 and a packet synchronization code detector 242.

As described above, in the communication device 200 according to the present embodiment, when the error detection circuit 240 determines that the received signal waveform is lower than a predetermined quality, for example, the output control signal S240 causes the antenna circuit 210 to The front-end parameter of the component related to the communication function, that is, any one of the inductance L11 of the antenna coil 211, the resistance value R11 of the resistance component 212, the capacitance C11 of the capacitor 213, and the capacitance Ct of the capacitor 214a of the matching circuit 214 Control is performed so as to change by a preset value.
Only one target element or a plurality of target elements may be controlled at the same time, but usually L1, C1, and R1 are values directly related to the antenna coil shape, which makes control complicated. A case where the capacitance Ct of the capacitor 214a of the matching circuit 214 that can be easily controlled is changed will be described below as an example.

Assuming that the IC card 120 and the R / W are in a null state as shown in FIG. 3A or B in FIG. 5, the signal receiving circuit 230 cannot normally receive the load modulation signal from the IC card 120 side. Therefore, the error detection circuit 240 detects the “error state”.
There are various methods for displaying the error state. In the simplest case, an error is output as 1-bit logic information, and every time an error is detected, “1/0” of the output logic signal is inverted. The method can be adopted.
Based on the “1” / “0” information, the value of the capacitance Ct of the capacitor 214a of the RLC matching circuit 214 is changed in two stages.
By appropriately selecting and setting the two-stage value of Ct to be changed, it is possible to shift from a null error state to a normal reception state avoiding this.

FIG. 16 shows a load modulation waveform detected on the R / W side when only the value of Ct is changed from Ct = 40 pF to 44 pF under exactly the same conditions as in FIG. 5, that is, the change in V1 = ΔV1. It is a thing.
Compared with FIG. 5, the null at k = 0.2 when Ct = 40 pF moves to k = 0.15 at Ct = 44 pF, and at the position of k = 0.2, which was the original null. It turns out that the signal of a reverse phase has changed into the state which can fully receive.

  Any specific method for controlling and changing the value of Ct may be used, but as a simple method, a method using a variable capacitance diode element whose capacitance value changes according to an externally applied voltage can be employed.

  As another method, for example, as shown in FIG. 17, two types of capacitors 214A-1 and 214A-2 having capacitances Ct1 and Ct2 are switched by a switch (SW) 215A, or in series as shown in FIG. For example, a method of short-circuiting one of the two connected capacitors 214B-1 and 214B-2 with the switch 215B can be employed.

In this case, the total capacitance value Ct is the capacitance Ct1 of the capacitor 214A-1 when the switch 215A is on the upper side in the configuration of FIG. 18, the capacitance Ct2 of the capacitor 231A-2 when the switch 215A is on the lower side, and the switch 215B is on in the configuration of FIG. When Ct1 is off, Ct1 * Ct2 / (Ct1 + Ct2) is obtained.
In any case, the value of k at which null occurs, that is, the distance range is a very narrow range, so that the normal communication state can be switched by slightly changing the element value.

  In the above example, the configuration in which the element value is switched to only binary has been described, but the same effect can be achieved even by switching multiple values of three or more values. In some cases, the detection result of the error detection circuit A higher effect can also be expected by taking a means of performing multi-stage evaluation and switching to the one with the best communication characteristics.

In the above example, the RLC matching circuit is configured by only one element of the capacitor Ct. However, depending on selection of element values of L1 and C1, as shown in FIGS. 19A to 19C, the capacitor Instead of this, an inductor element can be used, and in some cases, for example, a plurality of capacitors, an inductor 216, and a resistor element 217 can be combined.
In the case of a plurality of elements, only a specific one of them may be changed, or a plurality of elements may be changed simultaneously.

  In the present embodiment, a mobile phone has been described as an example of the information device. However, the present invention can be applied to other mobile terminals (PDA, etc.) or personal computers.

As described above, in the upstream direction (from card to R / W) communication of a proximity IC card, so-called load modulation that performs data communication by changing the voltage at the antenna end of the reader / writer by switching the load resistance value in the card. However, there is a distance (null point) where load modulation is theoretically not applied.
In this embodiment, in order to avoid this null point, the quality of the received waveform is inspected on the reader / writer side. When the quality deteriorates, the value of either the antenna tuning circuit or the LCR element of the matching circuit is changed. Communication quality can be improved by controlling to escape the null point.

2 shows an example of the basic configuration of an R / W and an IC card. It is a figure which shows notionally the relationship between a load modulation signal and the voltage V1 of the both ends of the antenna coil by the side of R / W, Comprising: When a load resistance value becomes small, it is a figure which shows the case where the voltage V1 also becomes small. It is a figure which shows notionally the relationship between a load modulation | alteration signal and the voltage V1 of the both ends of the antenna coil of R / W side, Comprising: It is a figure which shows the null state where the value of voltage V1 does not change even if load resistance value changes. . It is a figure which shows notionally the relationship between a load modulation signal and the voltage V1 of the both ends of the antenna coil by the side of R / W, Comprising: It is a figure which shows the case where the voltage V1 becomes large when load resistance value becomes small. It is a figure which shows the load modulation waveform detected by the R / W side in case of fc = 13.56MHz, Ct = 40pF, C1 = 30pF, L1 = 1530nH, L2 = 1200nH, RL = 1kΩ. It is a figure which shows the structural example of the communication system with which the mobile telephone as a portable information device which concerns on embodiment of this invention is applied. It is a block diagram which shows the basic structural example of the mobile telephone which concerns on this embodiment. It is a figure which shows the example of 1 structure of the communication apparatus incorporating the R / W function mounted in the mobile telephone which concerns on embodiment of this invention. It is a circuit diagram which shows the structural example of the IC card which concerns on this embodiment. It is a figure which shows the example of a format of the packet data applied to proximity IC card communication. It is a figure which shows an example of the judgment logic of the quality of Manchester code | cord waveform. It is a figure which shows the example of front end parameter control by determination of data waveform quality. It is a figure which shows the example of front end parameter control by determination of data error detection. It is a figure which shows the example of front end parameter control by determination of reception failure. It is a block diagram which shows the structural example of the error detection circuit which concerns on this embodiment. 5 shows the load modulation waveform detected on the communication device (R / W) side when only the Ct value is changed from Ct = 40 pF to 44 pF under the same conditions as in FIG. 5, that is, the change in V1 = ΔV1. FIG. It is a figure which shows the 1st switching structural example of the capacitance value of a matching circuit. It is a figure which shows the 1st switching structural example of the capacitance value of a matching circuit. It is a figure which shows the other structural example of a matching circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Communication system, 110 ... Mobile phone, 115 ... Memory part, 116 ... Communication apparatus, 117 ... Control part, 120 ... Non-contact type IC card, 130 ... Base , 140 ... communication network, 150 ... server, 200 ... communication device, 210 ... antenna circuit, 211 ... antenna coil, 212 ... series resistance component, 213 ... capacitor, 214, 214A to 214E ... matching circuit, 214a, 214A-1, 214A-2, 214B-1, 214B-2, 214D-1, 214D-2, 214E-1, 214E-2 ... capacitor, 216 ... Inductor, 217 ... Resistance, 220 ... Carrier signal source (OSC), 230 ... Signal receiving circuit, 240 ... Error detection circuit, 241 ... Data shaping 2411 ... Data phase detector 2412 ... Data quality determiner 242 ... Packet synchronous code detector 243 ... Packet data output device 244 ... Intra-packet data error detector 245 ... Front-end parameter adjusters.

Claims (17)

An antenna circuit including at least an antenna inductor as a component related to communication;
A carrier signal source connected to the antenna circuit for driving the antenna inductor of the antenna circuit and generating a carrier of a predetermined frequency;
A signal receiving circuit for receiving and demodulating the signal induced in the antenna inductor;
An error detection circuit having a function of detecting a signal error of the demodulated output of the signal receiving circuit,
The antenna circuit is formed such that at least one element value of the constituent elements can be changed,
The error detection circuit controls to change at least one element value of a constituent element involved in communication of the antenna circuit by a predetermined amount when a signal error is detected. The error detection circuit determines whether or not the waveform quality of the demodulated signal of the signal receiving circuit is good, and controls to change the element value by a predetermined amount when it is determined that the waveform quality is not good. The communication device described. The communication apparatus according to claim 1, wherein the error detection circuit determines whether or not there is an error in data in the received signal, and controls the element value to change by a predetermined amount when there is a data error. 2. The communication according to claim 1, wherein the error detection circuit determines a reception failure based on a signal transmission / reception content / history, and controls to change the element value by a predetermined amount when the reception failure is determined. apparatus. The error detection circuit is
A first processing unit that determines whether or not the waveform quality of the demodulated signal of the signal receiving circuit is good and that the element value is changed by a predetermined amount when it is determined that the waveform quality is not good;
A second processing unit that determines whether or not there is an error in the data in the received signal, and controls the element value to change by a predetermined amount when there is a data error, and from the contents and history of signal transmission / reception A third processing unit for determining a reception failure and controlling the element value to change by a predetermined amount when it is determined that the reception has failed;
The communication apparatus according to claim 1, further comprising at least one processing unit. The antenna circuit is
A tuning capacitor that forms a tuning circuit with the antenna inductor;
The communication device according to claim 1, wherein the error detection circuit controls at least one of an inductance of the antenna inductor and a capacitance of the tuning capacitor to change by a predetermined amount when a signal error is detected. . The antenna circuit includes a matching circuit connected to the antenna inductor and the carrier signal source,
The matching circuit includes at least one component of an inductor, a capacitor, and a resistor,
When the error detection circuit detects a signal error, at least one of an inductance value of the antenna inductor, a capacitance of the tuning capacitor, and an element value of at least one component of the matching circuit is changed by a predetermined amount. The communication device according to claim 6, wherein the communication device is controlled to perform. The communication apparatus according to claim 1, wherein the signal received by the antenna circuit includes a load modulation signal. An information device having an information processing function,
Including a communication device having a reader / writer function,
The communication device is
An antenna circuit including at least an antenna inductor as a component related to communication;
A carrier signal source connected to the antenna circuit for driving the antenna inductor of the antenna circuit and generating a carrier of a predetermined frequency;
A signal receiving circuit for receiving and demodulating the signal induced in the antenna inductor;
An error detection circuit having a function of detecting a signal error of the demodulated output of the signal receiving circuit,
The antenna circuit is formed such that at least one element value of the constituent elements can be changed,
The error detection circuit controls to change at least one element value of a component element involved in communication of the antenna circuit by a predetermined amount when a signal error is detected. The error detection circuit determines whether or not the waveform quality of the demodulated signal of the signal receiving circuit is good and controls to change the element value by a predetermined amount when it is determined that the waveform quality is not good. Information equipment described. The information device according to claim 9, wherein the error detection circuit determines whether or not there is an error in data in the received signal, and controls the element value to change by a predetermined amount when there is a data error. The information according to claim 9, wherein the error detection circuit determines a reception failure from the content / history of signal transmission / reception, and controls the element value to change by a predetermined amount when it is determined that the reception has failed. machine. The error detection circuit is
A first processing unit that determines whether or not the waveform quality of the demodulated signal of the signal receiving circuit is good and that the element value is changed by a predetermined amount when it is determined that the waveform quality is not good;
A second processing unit that determines whether or not there is an error in the data in the received signal, and controls the element value to change by a predetermined amount when there is a data error, and from the contents and history of signal transmission / reception A third processing unit for determining a reception failure and controlling the element value to change by a predetermined amount when it is determined that the reception has failed;
The information device according to claim 9, further comprising at least one processing unit. The antenna circuit is
A tuning capacitor that forms a tuning circuit with the antenna inductor;
The information device according to claim 9, wherein the error detection circuit controls at least one of an inductance of the antenna inductor and a capacitance of the tuning capacitor to change by a predetermined amount when a signal error is detected. . The antenna circuit includes a matching circuit connected to the antenna inductor and the carrier signal source,
The matching circuit includes at least one component of an inductor, a capacitor, and a resistor,
When the error detection circuit detects a signal error, at least one of an inductance value of the antenna inductor, a capacitance of the tuning capacitor, and an element value of at least one component of the matching circuit is changed by a predetermined amount. The information device according to claim 14, wherein the information device is controlled to perform. The information device according to claim 9, wherein a signal received by the antenna circuit includes a load modulation signal. The information device according to any one of claims 9 to 15, wherein the information processing function includes a communication function.

Images